Sensory shelf life analysis allows to identify the ideal period for consumption of a product. It is available in Excel using the XLSTAT statistical software.
What is sensory shelf life analysis
Sensory shelf life analysis is used to evaluate the ideal period for consumption of a product using sensory evaluation of assessors at different times/dates.
It may happen that the physico-chemical properties of a product are not sufficient to assess the quality of a product with respect to the period in which it is consumed. Frequently, adding sensory evaluation of the product will highlight the best consumption period. In the example of a yogurt, you may have a product that is suitable for consumption but in a sensory evaluation will be too acid or after a certain period will look less attractive.
Methods conventionally used in the analysis of survival data are applicable in this case.
Generally, when conducting this type of sensory tests, the assessors taste the same product at different times/dates. This can be done in different sessions, but it is generally recommended to prepare a protocol that allows to obtain products with different seniority for the test day.
Each assessor will express its opinion on the tested product (like / do not like) and we thus obtain a table of preferences per assessor for each date.
As the exact dates the assessor has change his preference are not known, we use the notion of censoring to set these dates. Thus, if preferences have been collected each week, if an assessor does not like a product after 3 weeks, this assessor is censored by interval between the 2nd and 3rd week. Assume that an assessor appreciates the product all long the study, this assessor is right censored at the last date of the study. Finally, if the assessor likes the product then does not like it and likes it again later in the study, we consider this assessor is left censored at the last date he changed his preference.